The ubiquitin-conjugating enzyme CDC34 is essential for cytokinesis in contrast to putative subunits of a SCF complex in Trypanosoma brucei

MANFRED AUER; BUÀ JACQUELINE; TÈLLEZ- IÑÒN M.TERESA; JEREMY C. MOTTRAM; RICHARD BURCHMORE; BRIARDO LLORENTE; JOANNA KOSZELA; ROJAS F.,

PLOS NEGLECTED TROPICAL DISEASES

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2017 vol. 11 p. 1 - 22

1935-2735

The ubiquitin-proteasome system is a post-translational regulatory pathway for controllingprotein stability and activity that underlies many fundamental cellular processes, includingcell cycle progression. Target proteins are tagged with ubiquitin molecules through theaction of an enzymatic cascade composed of E1 ubiquitin activating enzymes, E2 ubiquitinconjugating enzymes, and E3 ubiquitin ligases. One of the E3 ligases known to be responsiblefor the ubiquitination of cell cycle regulators in eukaryotes is the SKP1-CUL1-F-box complex(SCFC). In this work, we identified and studied the function of homologue proteins ofthe SCFC in the life cycle of Trypanosoma brucei, the causal agent of the African sleepingsickness. Depletion of trypanosomal SCFC components TbRBX1, TbSKP1, and TbCDC34by RNAi resulted in decreased growth rate and contrasting cell cycle abnormalities for bothprocyclic (PCF) and bloodstream (BSF) forms. Depletion of TbRBX1 in PCF cells interferedwith kinetoplast replication, whilst depletion of TbSKP1 arrested PCF and BSF cells in theG1/S transition. Silencing of TbCDC34 in BSF cells resulted in a block in cytokinesis andcaused rapid clearance of parasites from infected mice. We also show that TbCDC34 isable to conjugate ubiquitin in vitro and in vivo, and that its activity is necessary for T. bruceiinfection progression in mice. This study reveals that different components of a putativeSCFC have contrasting phenotypes once depleted from the cells, and that TbCDC34 is essentialfor trypanosome replication, making it a potential target for therapeutic intervention